Allow AuthAdapters to be constructed

[dblythy]

New Feature / Enhancement Checklist

• I am not disclosing a vulnerability.
• I am not just asking a question.
• I have searched through existing issues.

Current Limitation

Currently, the AuthAdapter class is not exported by Parse Server, meaning developers cannot extend it to their own custom auth

Feature / Enhancement Description

Export AuthAdapter

Example Use Case

Alternatives / Workarounds

3rd Party References

[parse-github-assistant]

Thanks for opening this issue!

• 🎉 We are excited about your ideas for improvement!

[parseplatformorg]

🎉 This change has been released in version 6.1.0-alpha.1

[parseplatformorg]

🎉 This change has been released in version 6.1.0-beta.2

[parseplatformorg]

🎉 This change has been released in version 6.1.0